The present invention relates to novel diphenyl ether compounds and novel herbicides containing at least one of the compounds as an active ingredient.
A number of diphenyl ether compounds have heretofore been studied for their practical use as herbicides, but these compounds are, in many cases, much different in the herbicidal activity, the developing manner, the selectivity, the durability of efficacy, etc., depending on slight differences in the chemical structures such as the kind, number and position of their substituents, and it is very difficult to anticipate the herbicidal activity of compounds from the similarity of the chemical structures of compounds.
As disclosed in e.g. U.S. Pat. No. 3,316,080 and Japanese Patent Publication No. 9898/1963, it is well-known that some of diphenyl ether compounds have superior herbicidal activities. For example, 2,4,6-trichloro-4'-nitrodiphenyl ether and 2,4-dichloro-3'-methoxy-4'-nitrodiphenyl ether have been broadly used as herbicides for initial period paddy field.
However, since these compounds are insufficient in the residual efficacy and inconvenient in that it is difficult to completely control weeds when their use time is missed, it has been desired to develop herbicides for paddy field, having a higher herbicidal activity and a safer selectivity than those of the above-mentioned known diphenyl ether compounds, and also a herbicidal activity capable of controlling perennial weeds of paddy field which are difficult to control.
On the other hand, 2,4-dichloro-4'-nitrodiphenyl ether has been broadly used as a herbicide for dry field crops, and besides, certain diphenyl ether compounds have been known, but since these compounds are insufficient in the efficacy against broad-leaved weeds, it has been also desired to develop herbicides for dry field crops, having a higher herbicidal activity and a safer selectivity than those of these known diphenyl ether compounds.